Case summary:

An ALS crew responded to a 70s man with shortness of breath.  They found the patient seated  but he was cool, pale and diaphoretic.  Patient was placed on the monitor and he had the following initial set of vitals:

Vitals: BP 120/85,  HR 174,  RR 22,  Sat 97%,  glucose 181

The crew obtained a 12-lead EKG given the heart rate which is included below.

They interpreted this rhythm as a narrow complex, regular tachycardia without any p-waves present.  They correctly diagnosed this as a stable supraventricular tachycardia (SVT).  The crew extricated the patient to the ambulance.  They then placed and IV and administered adenosine in order to try and chemically cardiovert the rhythm.  This was unsuccessful and after this initial attempt, the patient’s BP dropped to 76/43.  The crew identified that this was now an unstable SVT and proceeded with electrical cardioversion immediately.  After the shock, the patient converted to a sinus rhythm and he had the following vitals:

Vitals: BP 148/91,  HR 116,  RR 20,  Sat 98%

Patient was transported to the receiving facility and remained well then entire remainder of the trip.

Highlights of the case:

Electrical cardioversion is the treatment for unstable SVT

This patient was correctly diagnosed with a stable SVT by this crew.  The treatment for stable SVT is to place pads on the pads (in case they become unstable) and place a good proximal IV to administer adenosine.  While we are placing the pads and the IV, we can have the patient do vagal maneuvers since this might be all it takes to convert the patient.  The good news is that the majority of patients with SVT are likely going to be stable.  However, if the patient is unstable, such as having crushing chest pain, pulmonary edema, or hypotension, the treatment is electrical cardioversion.  The older patients get and the faster the rate of the SVT, the higher the likelihood that the patient will be unstable if they go into this rhythm.  This patient started off stable but soon became unstable, so the crew correctly pivoted to electrical cardioversion.  The key with these patients is to always be prepared for them to become unstable and have the pads already in place to quickly deliver the shock if indicated. 

Sedation prior to electrical cardioversion for unstable arrythmias

Electrical cardioversion can be very distressing for patients.  We should attempt to sedate them prior to shocking them whenever possible.  Many protocols (including ours) cautions crews from using sedation if the patient is hypotensive.  However, we are often only shocking patients IF they are hypotensive.  This creates a catch-22 where we then never sedate these patients.  Given that the patient is hypotensive due to the arrythmia and that shocking them will rapidly correct this arrythmia (therefore correcting the BP), I recommend sedating just about every patient who is conscious enough to be aware of what is happening (even if the BP is low).  Some patients are so obtunded from the hypotension that they are unaware of what is going on.  For these patients, we do not need to sedate them since they are effectively “sedated” from decreased cerebral perfusion from the cardiogenic shock caused by the arrythmia.  For all others, we should really be sedating them prior to electrical cardioversion unless there is a compelling reason not to.